For the treatment of tinea unguium of nail, generally hitherto adopted is a method in which a liquid antifungal agent for external use is applied to a surface of the nail or a method in which an antifungal agent is orally administered. An antifungal agent for external use does not penetrate into the nail unless it is dissolved in a solvent. The kind of a usable solvent is, however, restricted. Further, even a usable solvent is feasible, its efficiency is low because the solubility of the agent in the solvent is very low, namely about 2% at maximum.
Thus, mere application of a conventionally employed antifungal agent for external use to a surface of the nail cannot obtain sufficient effect of penetration thereof into the nail because the solvent is readily evaporated and, therefore, the viscosity thereof increases. A nail has a hard tissue composed of walls of bricks of keratin, which is a protein, and does not have sebaceous gland or sweat gland. Therefore, neither sweat nor sebum, which might act as the solvent, is secreted from the nail. Moreover, the nail has a three-layered structure in which the outermost surface layer is hard. When a liquid antifungal agent for external use dissolved in a solvent is applied to the nail, therefore, it takes a long time for the antifungal agent for external use to penetrate from the surface of the nail into a deep part thereof. During the course of the penetration, the solvent is evaporated so that it becomes more difficult for the antifungal agent to penetrate into the nail.
It is also known to use a dry-type tape, such as a transdermal absorbing tape, that is generally used in patients suffering from asthma or cardiopathy, for the treatment of tinea unguium. Because a suitable solvent for use in such a transdermal absorbing tape is not available, however, the antifungal agent is not maintained in a dissolved state and cannot be transferred to a deep part of the nail. A nail lacquer-type method is also known in which the property of a manicure coated on a nail that the surface of the coating dries first and the portion in contact with the nail dries last is utilized to cause an antifungal agent for external use contained therein to penetrate into the nail before the drying thereof is completed. An antifungal agent for external use that is suitable for such a method is also known. This method, however, is not very effective to cause the antifungal agent for external use to penetrate deep into the nail, because the solvent used therein rapidly evaporates. A further method is known in which a gauze impregnated with a liquid antifungal agent for external use is placed on a nail and a finger cot is then closely fitted over the entire finger. With this method, however, since the organic solvent and the antifungal agent for external use which are impregnated in the gauze are held for a long time in contact with a skin part other than nail, skin irritation is often caused.
In addition, since the conventional devices used in the foregoing methods are not of a completely sealing type, the solvent for the antifungal agent for external use may leak around the intended location. Therefore, it is not possible to precisely judge whether an effective amount of the antifungal agent for external use has penetrated into a deep part of the nail. This may cause a problem of variation in the treatment effect. As a substitute for the above methods for applying an antifungal agent for external use onto a surface of the nail, a method is proposed in which an oral antifungal agent is administered. However, since the absorbing rate of such a medicine is very low because of its inherent property, there is a case in which the antifungal agent is not at all transferred to the nail by administration depending upon cases. Thus, this method has a problem that a sufficient effect is not obtainable. Further, there is an interindividual difference in the effect of treatment of tinea unguium by an oral antifungal agent. Moreover, it is necessary to continue the treatment until the nail has been healed completely, i.e. generally for a period of as long as about one year. Therefore, this method has further problems that the treatment is not freely applicable to patients with basic diseases or pregnant women due to side effects of the medicine and treatment costs inevitably increase.
As a substitute for the aforementioned methods, there have been proposed the following devices that can permit an antifungal agent for external use to penetrate into a deep part of a nail:
a device for promoting penetration of an antifungal agent into a deep part of a nail, which has an ultrasonic wave generation element for directly irradiating an ultrasonic wave generated therefrom to an ultrasonic wave transmission medium disposed in contact with a surface of the nail to which a required amount of an antifungal agent for external use has been previously applied (Patent Document 1);an athlete's foot treating apparatus including an electromagnetic wave oscillator for oscillating a gigahertz band electromagnetic wave and an emitting part for emitting the gigahertz band electromagnetic wave, wherein the emitting part is directed toward the affected area for irradiation thereof to heat sterilize Trichophyton in the horny layer and inside and back side of the nail (Patent Document 2); and
an athlete's foot treating device including a container containing a liquid in which the affected area is to be immersed, heating means for heating the liquid, means for forcibly circulating the liquid, a temperature sensor for measuring the temperature of the liquid, and controlling means for controlling the heating means based on the temperature measured by the temperature sensor, whereby when the affected area is immersed in the liquid having a controlled temperature, the body temperature in a deep region is increased so that thermotherapeutic permeation effect achieved. (Patent Document 3). These apparatuses are, however, large in size and expensive.
As described in the foregoing, the conventionally known methods for externally treating tinea unguium are not very effective. There are no external medicines for treating tinea unguium which are admitted by the Ministry of Health, Labor and Welfare, Japan. Further, only a few kinds of oral medicines are admitted by the Ministry of Health, Labor and Welfare, Japan for use in clinical sites for the treatment of tinea unguium. The present applicant has filed an application for a patent pertaining to a device for treating tinea unguium which device is to solve the aforementioned problems and which device can permit an antifungal agent for external use to efficiently penetrate into a deep part of the nail by applying, to a surface of the nail infected with Trichophyton, a liquid of the antifungal agent for external use dissolved in a solvent (Japanese patent application No. 2008-292958).
The present invention includes the above invention.